A trigeminal conditioned stimulus yields fast acquisition of cerebellum-dependent conditioned eyeblinks

• Published in: Behavioural brain research Vol. 226; no. 1; pp. 189 - 196
• Main Authors: Carrel, Andrew J., Zbarska, Svitlana, Zenitsky, Gary D., Bracha, Vlastislav
• Format: Journal Article
• Language: English
• Published: Shannon Elsevier B.V 01-01-2012; Elsevier
• Subjects: Animals; Behavioral psychophysiology; Biological and medical sciences; Cerebellum; Cerebellum - physiology; Classical conditioning; Conditioning, Classical - physiology; Conditioning, Eyelid - physiology; Fundamental and applied biological sciences. Psychology; Interposed nuclei; Male; Mystacial vibrissae; Psychology. Psychoanalysis. Psychiatry; Psychology. Psychophysiology; Rabbit; Rabbits; Vibrissae - physiology; Cerebellum; Rabbit; Interposed nuclei; Classical conditioning; Mystacial vibrissae; Stimulus; Central nervous system; Lagomorpha; Encephalon; Learning; Vertebrata; Mammalia; Acquisition process; Animal; Blinking; Vibrissa
• ISSN: 0166-4328; 1872-7549
• DOI: 10.1016/j.bbr.2011.09.010

► Eyeblink conditioning in rabbits is slow when using traditional auditory stimuli. ► We found that more natural trigeminal vibrissal stimulation yields faster learning. ► Trigeminal stimulus-evoked conditioned blinks are a result of associative learning. ► Trigeminal stimulus-evoked conditioned responses are cerebellum-dependent. ► Trigeminal vibrissal conditioning is well suited for studies of motor learning.
Classical conditioning of the eyeblink response in the rabbit is a form of motor learning whereby the animal learns to respond to an initially irrelevant conditioned stimulus (CS). It is thought that acquired conditioned responses (CRs) are adaptive because they protect the eye in anticipation of potentially harmful events. This protective mechanism is surprisingly inefficient because the acquisition of CRs requires extensive training – a condition that is unlikely to occur in nature. We hypothesized that the rate of conditioning in rabbits could depend on CS modality and that stimulating mystacial vibrissae as the CS could produce CR acquisition faster than the traditional auditory or visual stimulation. We tested this hypothesis by conditioning naïve rabbits in the delay paradigm using a weak airpuff CS (vCS) directed to the ipsilateral mystacial vibrissae. We found that the trigeminal vCS yields significantly faster CR acquisition. We next examined if vCS-evoked CRs are dependent on the intermediate cerebellum in the same fashion as CRs evoked by the traditional auditory CS. We found that vibrissal CRs could be abolished by inactivating the cerebellar interposed nuclei (IN) with muscimol. In addition, injections of picrotoxin in the IN shortened the onset latency of vibrissal CRs. These findings suggest that the tone and vCS-evoked CRs share similar cerebellar dependency.